2 KINGS 11
Among the many events divinely recorded in the history of Israel, one of the most remarkable is the interregnum of Athaliab-her usurpation, reign, and destruction-with the consequent restoration of the house of David. It is unique, no such circumstance occurring before or after. *
1 And when Athaliah the mother of Ahaziah saw that her son was dead, she arose and destroyed all the seed royal.
The royal house had been depleted by Jehoram's murder of his brothers, by Arab marauders, and by Jehu's execution of the "brethren of Ahaziah," but obviously he had left behind other sons and nephews whom Athaliah now determined to destroy.
Who was Athaliah? Where did she come from? And how came she to be Queen of Judah?
She was wife to Jehoram, King of Judah; daughter of Ahab, King of Israel. Jehoram was son of, and successor to Jehoshaphat, late King of Judah.
The characters of these two kings-fathers respectively of Athaliah and her husband - and their relationship to each other, must first engage our attention. From this we shall be able to ascertain how so disastrous a state obtained in Zion. *
3 And he was with her hid in the house of Yahweh 6 years. And Athaliah did reign over the land.
...we are impressed at once by the spectacle-a woman sitting on the throne of David! And such a woman! No daughter of Sarah, but a Canaanitish idolater; a concretion of all that is detestable and abominable in the sight of the Deity reigning in Zion enthroned in Jerusalem. *
Bro Growcott - A woman on David's throne
21 Seven years old was Jehoash when he began to reign.
The king and the people were united as one: a picture of the kingdom with the removal of the Papal system.  The Millennial Peace Typed: vv. 20-21. Significantly the number seven appears at the beginning of the incident (v. 4), and now at the conclusion (v. 21), typical of Messiah's reign of perfection. GEM